Mu-mimo access point and user station including methods for multi-user group management

ABSTRACT

Embodiments of a MU-MIMO access point, user station and method for multi-user group management are generally described herein. In some embodiments, a MU-MIMO access point may assign a MU group identifier (GID) and a group member index (GMI) to each of a plurality of associated user stations. The MU-MIMO access point may transmit a MU-MIMO transmission that includes a plurality of spatial streams. The MU-MIMO transmission may be destined for the user stations of a single MU group indicated by a GID that is included within the MU-MIMO transmission. A subset of the spatial streams may be intended for each user station of the indicated MU group that is identified by the GID transmitted within the MU-MIMO transmission. A user station may use its assigned GMI along with an N sts  field in the MU-MIMO transmission to determine which of the spatial streams to demodulate.

This application is a continuation of U.S. patent application Ser. No.12/975,614, filed Dec. 22, 2010, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relateto multi-user (MU) multiple-input multiple-output (MIMO) (MU-MIMO)communication techniques. Some embodiments pertain to very-highthroughput (VHT) basic service sets (BSSs) configured to operate inaccordance with an IEEE 802.11 standard, such as the IEEE 802.11 acdraft standard.

BACKGROUND

MIMO communication techniques allow for the communication of more thanone spatial data stream. MU-MIMO techniques exploit the availability ofmultiple independent radio terminals in order to enhance thecommunication capabilities of each individual terminal. MU-MIMOtechniques use a space-division multiple access (SDMA) technique toallow a terminal to transmit to or receive from multiple terminals inthe same frequency band simultaneously.

Since a MU-MIMO transmission can include a limited number of spatialdata streams, one issue with MU-MIMO communications is managing thevarious terminals for configuring MU-MIMO transmissions. Thus, there aregeneral needs for MU-MIMO access points, user stations and methods formanaging user stations for MU-MIMO communications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a MU-MIMO network in accordance with someembodiments;

FIG. 2 is a functional block diagram of a MU-MIMO access point inaccordance with some embodiments;

FIG. 3 is a functional block diagram of a user station in accordancewith some embodiments;

FIG. 4 is an illustration of a MU-MIMO transmission in accordance withsome embodiments;

FIG. 5 illustrates MU group identifier (GID) signaling in accordancewith some embodiments;

FIG. 6 illustrates a GID management frame with a fixed-length frameformat in accordance with some embodiments; and

FIG. 7 illustrates a GID management frame with a variable-length frameformat in accordance with some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

FIG. 1 illustrates a MU-MIMO network 100 in accordance with someembodiments. MU-MIMO network 100 may include a MU-MIMO access point (AP)102 and a plurality of associated user stations (STA) 104. The accesspoint 102 and at least some of the user stations 104 may be configuredfor MU-MIMO communications in which the MU-MIMO access point 102 maytransmit MU-MIMO transmissions for reception by the MU-MIMO configureduser stations 104.

In accordance with embodiments, the MU-MIMO access point 102 may managegroups of two or more user stations 104 for MU-MIMO communications inwhich user stations 104 are assigned to one or more MU groups 106 forreceipt of a MU-MIMO transmission 105. These embodiments are describedin more detail below.

In accordance with embodiments, the MU-MIMO access point 102 may assigna MU group identifier (GID) 117 and a group member index (GMI) 111 toeach of a plurality of associated user stations 104. Each GID 117 may beassigned to a different MU group 106 of two or more of the associateduser stations 104. The assigned GMI 111 may indicate an ordinateposition of a user station 104 in an assigned MU group 106. The MU-MIMOaccess point 102 may also be configured to transmit a MU-MIMOtransmission 105 that includes a plurality of spatial streams 115 andone of the assigned GIDs 107. The MU-MIMO transmission 105 may bedestined for user stations 104 of a single MU group 106 that isindicated by the GID 107 that is included within the MU-MIMOtransmission 105. In these embodiments, a subset (i.e., one or more) ofthe spatial streams 115 may be intended for each user station 104 of theMU group 106 that is identified by the GID 107 transmitted within theMU-MIMO transmission 105. The GID 107, 117 and the GMI 111 may beinteger values.

The MU-MIMO transmission 105 may be a single transmission (e.g., asingle packet such as a PPDU) comprising a plurality of frames that areintended for more than one user station 104. The MU-MIMO transmission105 may include two or more spatial streams 115. In accordance withembodiments, the GID 107 transmitted within a MU-MIMO transmission 105may indicate for which MU group 106 of user stations 104 the MU-MIMOtransmission 105 is intended. As described in more detail below, a userstation's assigned GMI 111 may be used by a user station 104 of the MUgroup 106 to determine which subset of the spatial streams 115 isintended for the user station 104.

The MU-MIMO access point 102 may utilize a downlink (DL) SDMA techniqueto transmit at least the portion of the MU-MIMO transmission 105 thatincludes the one or more spatial streams 115. In some embodiments, theMU-MIMO network 100 may be a very-high throughout (VHT) base stationservice set (BSS) configured to operate in accordance with one of theIEEE 802.11 standards or proposed/draft standards, such as the IEEE802.11 ac proposed/draft standard.

In accordance with embodiments, based on the GID 107 received within theMU-MIMO transmission 105, a user station 104 may be configured todetermine whether or not it is a member of the MU group to determine ifit needs to demodulate one or more of the spatial streams 115 of areceived MU-MIMO transmission 105. Based on the GMI 111 previouslyassigned to the user station 104, the user station 104 may furtherdetermine which subset of the one or more of the spatial streams 115 inthe MU-MIMO transmission 105 to demodulate.

For example, user station 104B may be assigned a GID value of two and aGMI value of three. In these embodiments, when the user station 104Breceives a MU-MIMO transmission 105 that includes a GID value of two, itmay determine that the received MU-MIMO transmission 105 is intended forthe members of its MU-MIMO group and therefore that one or more of thespatial streams 115 of the MU-MIMO transmission 105 may be demodulated.The user station 104B may use its assigned GMI value of three todetermine which subset of the spatial streams 115 in the MU-MIMOtransmission 105 to demodulate. These embodiments are described in moredetail below.

In some embodiments, the MU-MIMO access point 102 may be configured toassign one or more GIDs 117 to a single user station 104 or update theone or more GIDs 117 of a single user station 104 by transmitting a GIDmanagement frame 103. GID management frame 103 may be intended for asingle user station 104 and may include a station ID (SID) 113, one ormore assigned GIDs 117, and a GMI 111 for each assigned GID 117. Theseembodiments are discussed in more detail below.

In some embodiments, the MU-MIMO access point 102 may also include anumber of spatial streams (N_(sts)) field 109 within the MU-MIMOtransmission 105. The N_(sts) field 109 may indicate the number ofspatial streams 115 (e.g., space-time streams) that a particular userstation 104 is to demodulate. A user station 104 may be configured touse the assigned GMI 111 that is associated with the GID 107 of aMU-MIMO transmission 105 to determine which portion of the N_(sts) field109 to read. The portion of the N_(sts) field 109 may indicate to theuser station 104 which subset of the spatial streams 115 of the MU-MIMOtransmission 105 to demodulate.

In some embodiments, the GMI 111 assigned to a user station 104 mayindicate the order of the spatial streams 115 to demodulate. Forexample, a GMI of two may indicate to a user station 104 to demodulatethe subset of spatial streams 115 indicated in a second position of theN_(sts) field 109.

Although FIG. 1 illustrates that MU groups 106 include user stations 104that are geographically nearer to each other, this is for illustrativepurposes only and is not a requirement as user stations 104 selected fora MU group 106 may be geographically dispersed. In accordance withembodiments, user stations 104 need only be separated by an inch or soto be able to receive through different spatial channels.

FIG. 2 is a functional block diagram of a MU-MIMO access point 200 inaccordance with some embodiments. The MU-MIMO access point 200 may besuitable for use as MU-MIMO access point 102 (FIG. 1). The MU-MIMOaccess point 200 may include, among other things, physical-layer (PHY)circuitry 204 for communicating with user stations 104 (FIG. 1) inaccordance with MU-MIMO techniques. The MU-MIMO access point 200 may beconfigured for transmitting a MU-MIMO transmission 105 (FIG. 1) using aplurality of spatially separate antennas 201.

In accordance with embodiments, the MU-MIMO access point 200 maymaintain a MU group assignment table 206 to identify the user stationsof each MU group 106 (FIG. 1). In some embodiments, the MU groupassignment table 206 may include GIDs 207 that are assigned to each userstation 104 and a GMI 211 associated with each assigned GID 207. Table206 may use a station ID (SID) 205 to identify each user station 104 ofan assigned group. The station ID 205 may be a MAC address of the userstation 104 although other identifiers may be used to uniquely identifyeach user station 104 that is associated with the MU-MIMO access point200.

In some embodiments, the MU-MIMO access point 200 may include anassignment block 208 to select associated user stations 104 forassignment to a MU group 106 and to assign a GID 207 to the userstations 104 of the selected MU group 106. In some embodiments, thestation ID 205 may be an association ID or a receiver MAC address,although this is not a requirement.

In accordance with embodiments, the MU-MIMO access point 200 may selectuser stations 104 for assignment to one or more MU groups 106 and mayassign one GID 207 for each assigned MU group 106. Each MU group 106 ofuser stations 104 may be is assigned a different GID 207. Some userstations, such as user stations 104A, may belong to more than one MUgroup 106.

In accordance with some embodiments, the MU-MIMO access point 200 mayqueue traffic for each MU group 106 of user stations 104 based on theassigned GIDs 207. In these embodiments, the MU-MIMO access point 200may select one of the GIDs 207 for which traffic has been queued andgenerate a MU-MIMO transmission 105 for the user stations 104 of theselected GID 207. The MU-MIMO transmission 105 may be configured toinclude the selected GID 207 and to include the traffic queued for theuser stations 104 of the selected GID 207.

In some embodiments, the MU-MIMO access point 200 may include queueblock 210 to queue traffic and select a GID 207 for which traffic isqueued. The PHY-layer circuitry 204 may be configured to generate theMU-MIMO transmission 105 for the stations of the selected MU group 106.In some embodiments, the MU-MIMO access point 200 may segregate thetraffic queued for the user stations 104 of the selected MU group 106for transmission within one or more spatial streams 115. The MU-MIMOaccess point 200 may also include the N_(sts) field 109 (FIG. 1) in thepreamble to indicate which subset of the spatial streams of the MU-MIMOtransmission 105 each user station 104 of the selected MU group 106 isto demodulate based on each user station's GMI 211.

In some embodiments, the MU-MIMO access point 200 may select userstations 104 for assignment to a MU group 106 based on channelcharacteristics. In these embodiments, user stations 104 with similarchannel characteristics may be assigned to the same MU group 106. Insome embodiments, the MU-MIMO access point 200 may group user stations104 into MU groups 106 for efficient traffic distribution to multipleusers simultaneously with a MU-MIMO transmission. The MU-MIMO accesspoint 200 may group user stations 104 in various combinations with otherstations for increased flexibility in creating MU-MIMO transmissions.

In some embodiments, the MU-MIMO access point 200 may add user stations104 to MU groups 106, may remove user stations 104 from MU groups 106,and may delete MU groups 106 as traffic patterns change and as channelcharacteristics change. These embodiments are described in more detailbelow.

As mentioned above, in some embodiments, the MU-MIMO access point 200may be configured to assign one or more GIDs 207 to a single userstation 104 or update the one or more GIDs 207 of a single user station104 by transmitting a GID management frame 103 (FIG. 1). The GIDmanagement frame 103 may include an assignment of one or more GIDs 207and an assignment of a GMI 211 for each of the one or more assigned GIDs207 assigned to a particular user station 104. The GID management frame103 may be a unicast frame that is addressed to the single user station104. In some embodiments, the GID management frame 103 may include astation identifier, such as an SID 205, indicating which user station104 that the GID management frame 103 is intended for.

Accordingly, a single GID management frame 103 may be used to assignmore than one GID 207 to a user station 104 (i.e., since a user station104 may be a member of more than one MU group 106) as well as to assigna GMI 211 for each assigned GID 207. In this way, an individual userstation 104 can be added to or deleted from a MU group 106 withoutaffecting the membership of other user stations 104 of the MU group 106.

In some embodiments, physical-layer circuitry 204 may be an IEEE802.11ac PHY, such as a WiFi radio, and may be configured for DL SDMAtransmissions. Although the term ‘access point’ has been used todescribe MU-MIMO access point 200, the term ‘base station’ may also besuitable. Although the MU-MIMO access point 200 is illustrated as havingseveral separate functional elements, one or more of the functionalelements may be combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,application specific integrated circuits (ASICs), radio-frequencyintegrated circuits (RFICs) and combinations of various hardware andlogic circuitry for performing at least the functions described herein.In some embodiments, the functional elements of the MU-MIMO access point200 may refer to one or more processes operating on one or moreprocessing elements.

In some embodiments, the MU-MIMO access point 200 may configure theMU-MIMO transmission 105 for transmission over a channel bandwidthcomprising a primary access channel having a fixed bandwidth and asecondary channel of variable bandwidth. The primary access channel mayhave a bandwidth of 20 MHz and the secondary channel may have abandwidth of up to seven 20 MHz portions of bandwidth to achieve a totalor maximum channel bandwidth of up to 160 MHz. The preamble of theMU-MIMO transmission 105 may be transmitted on each 20 MHz portion ofthe channel bandwidth.

In some embodiments, MU-MIMO access point 200 may utilize acarrier-sense multiple access/collision avoidance (CSMA/CA) protocol forchannel access. In these embodiments, the access channel that wins thetransmission opportunity (TXOP) may be the primary access channel. Insome embodiments, the primary and the secondary channels comprisenon-contiguous portions of spectrum. In other embodiments, the primaryand the secondary channels comprise contiguous portions of spectrum.

FIG. 3 is a functional block diagram of a user station 300 in accordancewith some embodiments. The user station 300 may be suitable for use asany of the user stations 104 illustrated in FIG. 1. User station 300 mayinclude, among other things, a GID table 302 and physical-layer (PHY)circuitry 304. Physical-layer circuitry 304 may be configured tocommunicate with a MU-MIMO access point, such as MU-MIMO access point102 (FIG. 1) and may use a plurality of spatially separated antennas301. The user station 300 may be configured to maintain the GID table302 therein to identify each of the one or more assigned GIDs 117(FIG. 1) as well as to identify a GMI 111 (FIG. 1) associated with eachassigned GID 117. In response to receipt of GID management frame 103(FIG. 1), the user station 300 may update the information in its GIDtable 302.

In these embodiments, upon receipt of a MU-MIMO transmission 105 (FIG.1), the user station 300 may be configured to index the GID 117 receivedin the MU-MIMO transmission 105 in its GID table 302 to determinewhether or not it is a member of the MU group 106 indicated by the valueof the GID 117. When the user station 300 is a member of the MU group106 indicated by the GID 117 received in the MU-MIMO transmission 105,the user station 300 may identify the GMI 111 associated with GID 117from the GID table 302. Based on the associated GMI 111, the userstation 300 may then determine which subset of the one or more of thespatial streams 115 (FIG. 1) to demodulate based on the N_(sts) field109 (FIG. 1) in the received MU-MIMO transmission 105.

In this way, the GID table 302 may be used as a look-up-table (LUT) todetermine whether or not the user station 300 is a member of aparticular MU group and to look up the GMI 111 that is associated with aMU group 106 in which it is a member. Accordingly, the user station 300can determine whether or not it needs to demodulate a subsequent portionof a MU-MIMO transmission 105 that includes the one or more spatialstreams 115. Furthermore, a user station 104 may determine which subsetof the spatial streams 115 of the MU-MIMO transmission 105 todemodulate. In this way, the user station 300 does not need to expendthe energy by demodulating subsequent portions of MU-MIMO transmission105 that are not intended for it.

In some embodiments, the GID 107 and the N_(sts) field 109 are includedwithin a preamble of the MU-MIMO transmission 105 that is configured tobe receivable by all of the associated user stations 104. In theseembodiments, the N_(sts) field 109 and the GID 107 may both be withinthe same signaling field, although this is not a requirement.

Although the user station 300 is illustrated as having several separatefunctional elements, one or more of the functional elements may becombined and may be implemented by combinations of software-configuredelements, such as processing elements including digital signalprocessors (DSPs), and/or other hardware elements. For example, someelements may comprise one or more microprocessors, DSPs, applicationspecific integrated circuits (ASICs), radio-frequency integratedcircuits (RFICs) and combinations of various hardware and logiccircuitry for performing at least the functions described herein. Insome embodiments, the functional elements of the user station 300 mayrefer to one or more processes operating on one or more processingelements.

FIG. 4 is an illustration of a MU-MIMO transmission 400 in accordancewith some embodiments. The MU-MIMO transmission 400 may be suitable foruse as MU-MIMO transmission 105 (FIG. 1). The MU-MIMO transmission 400may include an initial portion 410 which may comprise its preamble, anda subsequent portion 412 which may include the one or more spatialstreams 115. As illustrated in FIG. 4, the preamble of the MU-MIMOtransmission 400 may include a VHT signaling field, such as VHT-SIG-Afield 406. The GID 107 and the N_(sts) field 109 may be included withinthe VHT-SIG-A field 406 of the MU-MIMO transmission 400 as shown.

The MU-MIMO transmission 400 may also include legacy training fields(L-TFs) 402, non-HT signal field (L-SIG) 404, VHT training fields(VHT-TFs) 408, VHT-SIG B fields 414, service fields 415 and data fields416. Each data field 416 may correspond to one of the spatial streams115 of the PPDU.

The MU-MIMO access point 102 (FIG. 1) may be configured to transmit theinitial portion 410 that comprises the preamble in non-directional(e.g., substantially omnidirectional) fashion. The access point 102 maybe configured to transmit the subsequent portion 412 of the MU-MIMOtransmission 400 that includes the plurality of spatial streams 115 in adirectional fashion.

In these embodiments, the initial portion 410 that includes theVHT-SIG-A field 406 (which includes the GID 107 and the N_(sts) field109) that is transmitted in the non-directional fashion may beconfigured to be received by all associated user stations 104 (FIG. 1).The subsequent portion 412 that includes the plurality of spatialstreams 115, when transmitted in a directional fashion, may bebeamformed or precoded as described in more detail below.

A user station 104 may be configured to use an assigned GMI 111 (FIG. 1)that is associated with the GID 107 (FIG. 1) of the MU-MIMO transmission400 (read from the GID table 302 (FIG. 3)) to determine which portion ofthe N_(sts) field 109 (FIG. 1) to read. The portion of the N_(sts) field109 may indicate to the user station 104 which subset of the spatialstreams 115 of the MU-MIMO transmission 400 to demodulate. In someembodiments, the user station 104 may be configured to use the assignedGMI 111 to determine which three-bit portion of the N_(sts) field 109 toread.

In some of these embodiments, the MU-MIMO access point 102 may applybeamforming techniques for the transmission of the subsequent portion412. Beamforming coefficients for each spatial stream 115 may be basedon channel characteristics of the user stations 104 of the MU group 106that are to receive a particular spatial stream 115. The use ofdifferent beamforming coefficients for each spatial stream 115 allowseach user station 104 of the MU group 106 to separate the differentspatial streams 115 using signal processing techniques.

In some embodiments, the MU-MIMO access point 102 may precode thesubsequent portion 412 using codewords based on a codebook (e.g., aprecoding matrix) for beamforming. In these embodiments, channelestimation may be performed based on pilot signals transmitted by theMU-MIMO access point 102. Based on the channel information, a codewordthat results in the maximum signal-noise-ratio (SNR) and a channelquality indictor (CQI) value corresponding to the codeword may bedetermined by a user station 104. The codeword and CQI may be fed backto the MU-MIMO access point 102 and the MU-MIMO access point 102 mayconfigure the MU-MIMO transmission 400 for the user stations 104 of aselected MU group 106 based on the codewords and the CQI values. In someembodiments, the MU-MIMO transmission 400 may be configured based on thecodewords and the CQI values so that a predetermined performance metricof the system is achieved or maximized. In these embodiments, at leastthe subsequent portion 412 of the MU-MIMO transmission 400 may betransmitted with a plurality of spatially separate antennas 201 (FIG.2).

In some embodiments, a user station, such as user station 300 (FIG. 3),may refrain from demodulating the subsequent portion 412 of the MU-MIMOtransmission 400 when the GID 107 included in the MU-MIMO transmission400 is not assigned to the user station 300 that receives the MU-MIMOtransmission 400. In these embodiments, the MU-MIMO transmission 400 maybe discarded since it was not intended for that particular user station300.

In some embodiments, the MU-MIMO access point 102 may create a unique MUgroup 106 for each possible combination of user stations 104. This mayresult in a large number of MU groups 106 and a large GID table 302 whenthere is a high number of user stations 104 associated with the MU-MIMOaccess point 102 (i.e., because each user station 104 would be includedin many MU groups 106).

In other embodiments, multiple combinations of user stations 104 may usethe same GID to reduce the size of the GID table 302. When multiple userstation combinations use the same GID, user stations 104 receiving aMU-MIMO transmission 400 may end up demodulating spatial streams 115that are not intended for that user station 104. These frames may bediscarded. These embodiments that use many multiple user-stationcombinations may provide a trade-off between slightly increased powerconsumption for a reduction in the size of the GID table 302. In someembodiments, a MU group 106 may include a single user station 104.

In accordance with embodiments, the number of spatial streams 115 thatmay be included in the MU-MIMO transmission 400 may depend on, amongother things, the number of antennas 201 (FIG. 2) used by the MU-MIMOaccess point 102 for transmitting the MU-MIMO transmission 400. Forexample, when eight antennas 201 are used, up to eight spatial streams115 may be transmitted.

In some embodiments, the MU-MIMO transmission 400 may include a channelbandwidth parameter 418 to indicate the channel bandwidth used, aspace-time block coding parameter 420, and a modulation and codingparameter (not separately illustrated) to indicate a modulation andcoding scheme of subsequent portions of the MU-MIMO transmission 400 astransmitted over the channel bandwidth. In some embodiments, the MU-MIMOtransmission 400 may indicate which 20 MHz portions of the spectrumcomprise the channel bandwidth of the MU-MIMO transmission 400.

FIG. 5 illustrates MU-GID signaling in accordance with some embodiments.An access point 502 may correspond to MU-MIMO access point 102 (FIG. 1)and user station (STA) 504 may correspond to one of user stations 104(FIG. 1). As described above, the access point 502 may transmit a GIDmanagement frame 503 to assign one or more GIDs 117 (FIG. 1) to userstation 504 or update the one or more GIDs 117 of the user station 504.GID management frame 503 may correspond to GID management frame 103(FIG. 1). After transmitting the GID management frame 503 to the userstation 504, the access point 502 may be configured to delaytransmitting of a MU-MIMO transmission 505 that includes a GID 107(FIG. 1) that was assigned or updated by the GID management frame 503.

In these embodiments, the MU-MIMO transmission 505 that is delayedincludes the GID that was assigned to user station 504 (i.e., that hadone of its GIDs assigned or updated). This delay may be used toaccommodate any processing delay of user station 504 associated with,for example, decrypting the GID management frame 503 and installingupdates to the GID table 302 (FIG. 3).

In some embodiments, the delay may be a MU group addition delay 507 andmay follow the receipt of an acknowledgement (ACK) 506 from the userstation 504. The ACK 506 may be transmitted by the user station 504 toacknowledge receipt of the GID management frame 503. In someembodiments, MU group addition delay 507 may be a fixed or predeterminedamount. In other embodiments, the MU group addition delay 507 may bedetermined based on delay amounts provided by user stations 104associated with the MU-MIMO access point 102 (e.g., when a user station504 joins the VHT BSS).

In some embodiments, each user station 104 may provide a delay amountassociated with installing or updating its GID table 302. The provideddelay amount may be an upper bound on a station's processing delay. Theaccess point 502 may utilize a greatest of these delay amounts (i.e.,from the user station with the greatest delay) as the MU group additiondelay 507. In some embodiments, the delay amount may be provided by auser station 104 during association in a field of an association requestframe, although this is not a requirement.

In some alternate embodiments, as illustrated in FIG. 5, aftertransmitting the GID management frame 503 to the user station 504, theaccess point 502 may delay transmitting the MU-MIMO transmission 505until receipt of a GID assignment confirmation frame 508 from the userstation 504 for which the GID management frame 503 was intended. Inthese embodiments, user stations 104 may be configured to transmit a GIDassignment confirmation frame 508 to the MU-MIMO access point 502 when auser station 504 has successfully installed or updated its GID table 302based on the received GID management frame 503.

In some embodiments, the access point 502 may update entries for aparticular user station 104 listed in its MU group assignment table 206(FIG. 2) after transmitting the GID management frame 503. The accesspoint 502 may wait until an ACK 506 is received from the user station504 before transmitting the MU-MIMO transmission 505 to the user station504 using the updated table 206 to ensure that the user station 504received the GID management frame 503. In some alternate embodiments,the access point 502 may wait until a GID assignment confirmation frame508 is received from the user station 504 before transmitting theMU-MIMO transmission 505 using the updated table 206 to ensure that theuser station 504 has installed or updated its GID table 302.

In some embodiments, the access point 502 may wait until the ACK 506 isreceived from the user station 504 before the access point 502 updatesits table 206. In some embodiments, the access point 502 may wait untila GID assignment confirmation frame 508 is received from the userstation 504 before the access point 502 updates its table 206.

FIG. 6 illustrates a GID management frame 603 with a fixed-length frameformat 600 in accordance with some embodiments. GID management frame 603may be suitable for use as GID management frame 103 (FIG. 1) and mayhave a fixed-length frame format 600. In these embodiments, the GIDmanagement frame 603 may be configured to provide a full-table update toa user station's GID table 302 (FIG. 3). In these embodiments, the GIDmanagement frame 603 may include a membership bitmap field 602 and a GMIlookup table field 604. The membership bitmap field 602 may comprise abitmap in which each bit of the bitmap represents whether or not theuser station 300 (FIG. 3) is a member of a corresponding MU group. Theposition of each bit of the bitmap of the membership bitmap filed 602may be indexed by the GID. The GMI lookup table field 604 may indicatethe GMI for the user station 300 for an associated GID (i.e., for acorresponding MU group).

In the bitmap of the membership bitmap field 602, a bit that is set toone may indicate that the user station 300 is a member of the groupindicated by the position of the bit. For each bit that is set to one inthe membership bitmap field 602, the corresponding bit in the GMI lookuptable field 604 indicates the GMI value for the associated GID. Inresponse to receipt of the GID management frame 603, the user station300 may update its GID table 302 (FIG. 3) based on the information inthe membership bitmap field 602 and the corresponding information in theGMI lookup table field 604.

For example, the bit that is set to one in the fourth position of themembership bitmap field 602 (as shown in FIG. 6) indicates that the userstation 300 (for which the GID management frame 603 is intended) isassigned to be a member of the fourth MU group (i.e., GID=4). Thecorresponding GMI of two in the GMI lookup table field 604 indicatesthat the user station 300 should look at the second portion of theN_(sts) field 109 (e.g., B16 to B18 of the VHT-SIG-A field 406 (FIG. 4))for the number and order of the spatial streams 115 (FIG. 1) todemodulate. Each two bits of the GMI lookup table field 604 may indicatethe GMI of the user station for a corresponding MU group. In this way,the user station 300 can determine which subset of the spatial streams115 to demodulate based on a portion of the N_(sts) field 109.

In some embodiments, the membership bitmap field 602 may be eight octetslong and the GMI lookup table field 604 may be sixteen octets long,although this is not a requirement. There may be sixty-four GIDmanagement fields, each of which contains one bit to indicate themembership status of a user station in the corresponding MU group andtwo bits to indicate the group member index (GMI) of a station in thecorresponding MU group.

FIG. 7 illustrates a GID management frame 703 with a variable-lengthframe format 700 in accordance with some embodiments. GID managementframe 703 may be suitable for use as GID management frame 103 (FIG. 1)and may have a variable-length frame format 700. In these embodiments, aGID management frame 703, when configured in accordance with thevariable-length frame format 700, may provide additions, deletions orchanges to a user station's GID table 302 (FIG. 3). In response toreceipt of the GID management frame 703, the user station 300 (FIG. 3)may update its GID table 302.

In these variable-length frame format embodiments, the GID managementframe 703 may include a field 702 to indicate the number of entries tobe added to the GID table 302 followed by one or more fields 704 toindicate which entries are to be added (e.g., one octet per entry). Inthese embodiments, the GID management frame 703 may also include a field706 to indicate the number of entries to be deleted followed by a numberof fields 708 to indicate which entries are to be deleted (e.g., oneoctet per entry). In these variable-length frame format embodiments,each add entry element of field 704 may include a GID 710 of the MUgroup to which the user station 300 is being added or for which thestation's GMI is being changed as well as the new GMI 712 associatedwith that GID 710. Each delete entry element of field 708 may includethe GID of the MU group from which the user station 300 is beingremoved.

Embodiments may be implemented in one or a combination of hardware,firmware and software. Embodiments may also be implemented asinstructions stored on a computer-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. In some embodiments, themachine may include one or more processors and may be configured withinstructions stored on a computer-readable storage device.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims. The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

1. (canceled)
 2. An apparatus of an access point, the apparatuscomprising a memory and processing circuitry, the processing circuitryconfigured to: determine an assignment of an associated station to oneor more groups and a corresponding user position for each of the one ormore groups, wherein each of the one or more groups is associated with agroup identifier (ID); encode a group ID management frame to transmitthe assignment, wherein the ID management frame comprises a membershipstatus array, wherein the membership status array is an array of bitswith each bit indicating whether the associated station is a member ofthe group with the group ID equal to a first index of the array of bits,and wherein the group ID management frame further comprises a userposition array with two bits to indicate a user position of theassociated station for each of the corresponding one or more groups; andconfigure the access point to transmit the group ID management frame tothe associated station.
 3. The apparatus of claim 2, wherein the twobits indicate an ordinate position of the associated station in thecorresponding group with the group ID of a second index of the userposition array.
 4. The apparatus of claim 2, wherein the processingcircuitry is further configured to: decode an acknowledgement (ACK) fromthe associated station to acknowledge receipt of the group ID managementframe.
 5. The apparatus of claim 2, wherein the processing circuitry isfurther configured to: select a group of the one or more groups;determine a second assignment of a plurality of space-time streams forthe selected group based on user positions in the selected group of oneor more associated stations, wherein the selected group of one or morestations includes the associated station; and configure the access pointto transmit a multi-user multiple-input multiple-output (MU-MIMO)transmission to the selected group, the MU-MIMO transmission to includethe plurality of separate space-time streams and the group ID of theselected group, the plurality of separate space-time streams to betransmitted on a transmission bandwidth that comprises one or morechannels.
 6. The apparatus of claim 5, wherein each space-time stream ofthe plurality of space-time streams is for one of the one or moreassociated stations.
 7. The apparatus of claim 6, wherein the userposition of the associated station determines a subset of the pluralityof space-time streams to be transmitted to the associated station. 8.The apparatus of claim 7, wherein the MU-MIMO transmission comprises asimultaneous transmission of data packets to two or more stations of thegroup with the group ID.
 9. The apparatus of claim 5, wherein theMU-MIMO transmission further comprises a preamble comprising a bandwidthindicator and a number of the space-time streams that the associatedstation is to demodulate, the bandwidth indicator indicating thetransmission bandwidth of the plurality of space-time streams.
 10. Theapparatus of claim 5, wherein the one or more channels are each 20 MHz.11. The apparatus of claim 9, wherein the processing circuitry isfurther configured to: configure the access point to transmit thepreamble of the MU-MIMO transmission in a non-directional fashion, andwherein a subsequent portion of the MU-MIMO transmission includes theplurality of space-time streams and is transmitted in a directionalfashion.
 12. The apparatus of claim 2, wherein the group ID managementframe is a fixed length unicast frame that includes a membership statusarray field that is eight octets long and a user position array fieldthat is sixteen octets long.
 13. The apparatus of claim 2, furthercomprising: one or more antennas coupled to the processing circuitry.14. The apparatus of claim 1, wherein the access point is an Instituteof Electronical and Electronic Engineers (IEEE) 802.11 ac access point.15. A non-transitory computer-readable storage medium that storesinstructions for execution by one or more processors, the instructionsto configure the one or more processors to cause an access point to:determine an assignment of an associated station to one or more groupsand a corresponding user position for each of the one or more groups,wherein each of the one or more groups is associated with a groupidentifier (ID); encode a group ID management frame to transmit theassignment, wherein the ID management frame comprises a membershipstatus array, wherein the membership status array is an array of bitswith each bit indicating whether the associated station is a member ofthe group with the group ID equal to a first index of the array of bits,and wherein the group ID management frame further comprises a userposition array with two bits to indicate a user position of theassociated station for each of the corresponding one or more groups; andconfigure the access point to transmit the group ID management frame tothe associated station.
 16. The non-transitory computer-readable storagemedium of claim 15, wherein the two bits indicate an ordinate positionof the associated station in the corresponding group with the group IDof a second index of the user position array.
 17. The non-transitorycomputer-readable storage medium of claim 15, wherein the instructionsfurther configure the one or more processors to cause a wirelessapparatus to: decode an acknowledgement (ACK) from the associatedstation to acknowledge receipt of the group ID management frame.
 18. Thenon-transitory computer-readable storage medium of claim 15, wherein theinstructions further configure the one or more processors to cause awireless apparatus to: select a group of the one or more groups;determine a second assignment of a plurality of space-time streams forthe selected group based on user positions in the selected group of oneor more associated stations, wherein the selected group of one or morestations includes the associated station; and configure the access pointto transmit a multi-user multiple-input multiple-output (MU-MIMO)transmission to the selected group, the MU-MIMO transmission to includethe plurality of separate space-time streams and the group ID of theselected group, the plurality of separate space-time streams to betransmitted on a transmission bandwidth that comprises one or morechannels.
 19. A method performed by an access point (AP), the methodcomprising: determining an assignment of an associated station to one ormore groups and a corresponding user position for each of the one ormore groups, wherein each of the one or more groups is associated with agroup identifier (ID); encoding a group ID management frame to transmitthe assignment, wherein the ID management frame comprises a membershipstatus array, wherein the membership status array is an array of bitswith each bit indicating whether the associated station is a member ofthe group with the group ID equal to a first index of the array of bits,and wherein the group ID management frame further comprises a userposition array with two bits to indicate a user position of theassociated station for each of the corresponding one or more groups; andconfiguring the access point to transmit the group ID management frameto the associated station.
 20. The method of claim 19, the methodfurther comprising: selecting a group of the one or more groups;determining a second assignment of a plurality of space-lime streams forthe selected group based on user positions in the selected group of oneor more associated stations, wherein the selected group of one or morestations includes the associated station; and configuring the accesspoint to transmit a multi-user multiple-input multiple-output (MU-MIMO)transmission to the selected group, the MU-MIMO transmission to includethe plurality of separate space-time streams and the group ID of theselected group, the plurality of separate space-fl me streams to betransmitted on a transmission bandwidth that comprises one or morechannels.
 21. An apparatus of a station comprising a memory andprocessing circuitry coupled to the memory, the processing circuitryconfigured to: decode a group ID management frame comprising anassignment of the station to one or more groups and a corresponding userposition for each of the one or more groups, wherein each of the one ormore groups is associated with a group identifier (ID), and wherein theID management frame comprises a membership status array, wherein themembership status array is an array of bits with each bit indicatingwhether the station is a member of the group with the group ID equal toa first index of the membership status, and wherein the group IDmanagement frame further comprises a user position array with two bitsto indicate a user position of the station for each of the correspondingone or more groups; encode an acknowledgement frame to acknowledgereceipt of the group ID management frame; and configure the station totransmit the acknowledgement frame to an access point.
 22. The apparatusof claim 21, wherein the processing circuitry is further configured to:decode a preamble of a multi-user multiple-input multiple-output(MU-MIMO) transmission comprising a group ID; if a bit with an index ofgroup ID of the membership status array is set, determine one or morespace time streams of the MU-MIMO transmission are for the station basedon the user position of the user position array indexed by the group ID;and configure the station to receive the one or more space time streams.23. The apparatus of claim 21, wherein the MU-MIMO transmissioncomprises a simultaneous transmission of data packets to two or morestations of the group with the group ID.
 24. The apparatus of claim 21,wherein the MU-MIMO transmission further comprises a preamble comprisinga bandwidth indicator and a number of the space-time streams that theassociated station is to demodulate, the bandwidth indicator indicatingthe transmission bandwidth of the plurality of space-time streams. 25.The apparatus of claim 21, wherein the station is an Institute ofElectronical and Electronic Engineers (IEEE) 802.11ac access point. 26.The apparatus of claim 21, further comprising: one or more antennascoupled to the processing circuitry.